Clinical focus

Summary statement: new guidelines forthe management of paracetamolpoisoning in Australia and New Zealand

Alarge proportion of accidental paediatric expo-sures and deliberate self-poisoning incidentsinvolve paracetamol; it is the leading pharma-

ceutical agent responsible for calls to Poisons Informa-tion Centres in Australia and New Zealand.Management of paracetamol poisoning has altered sincethe previous guidelines were published in 2008, so thatthey do not reflect current practice by clinical toxicologists.The key changes from the previous guidelines concernthe indications for administration of activated charcoal;the management of patients taking large or massiveoverdoses; modified-release and supratherapeutic in-gestions; and paediatric liquid paracetamol ingestion.

Main recommendations

The management of patients with paracetamol overdoseis usually straightforward. Acute deliberate self-poisoning, accidental paediatric exposure and inadver-tent repeated supratherapeutic ingestions all requirespecific approaches to risk assessment and management.

Each initially involves a risk assessment (Box 1). The keyfactors to consider in paracetamol poisoning are theingested dose and serum paracetamol concentration(early), or clinical and laboratory features suggesting liverdamage (late). Serum paracetamol concentration shouldbe used to assess the need for acetylcysteine administra-tion in all patients presenting with deliberate self-poisoning with paracetamol, regardless of the stateddose. The management of acute paracetamol exposurewith known time of ingestion is summarised in a man-agement flow chart (Box 2) and the management ofsupratherapeutic ingestion is shown in Box 3.

It is important to note that the paracetamol treatmentnomogram has not changed, and that the acetylcysteineregimen remains the same as in the previous guidelines.

Changes in management

Gastric decontaminationIt was previously recommended that activated charcoalbe administered within 1 hour of paracetamol ingestion.The current guideline advises that 50 g activated charcoalshould be administered to a cooperative, awake adultwithin 2 hours of ingestion of a toxic dose of immediate-release paracetamol, and within 4 hours of modified-release paracetamol ingestion (Box 2).

For immediate-release paracetamol overdoses of greaterthan30g, activated charcoal shouldbe administeredup to

4 hours after ingestion. For massive modified-releaseparacetamol overdoses, absorption may continue until24 hours after ingestion, and patients may still benefitfrom activated charcoal treatment after more than4 hours.

Modified-release paracetamolAs per the previous guideline, acetylcysteine treatmentshould be started immediately if more than 200mg/kg or10 g (whichever is lower) has been ingested. Two assess-ments of serum paracetamol concentration 4 hours apartare required, the first at least 4 hours after ingestion.

The recommendation about when to discontinue ace-tylcysteine infusion has changed. Serial paracetamol con-centrations, measured 4 hours apart, must be below thenomogram line and decreasing. Further, near the comple-tion of acetylcysteine infusion (ie, 2 hours before comple-tion of infusion), serum alanine aminotransferase (ALT)and paracetamol concentrations should be measured.Acetylcysteine infusion should be continued if the ALTlevel is increasing (greater than 50 U/L) or the paraceta-mol concentration is greater than 10 mg/L (66 mmol/L).

Large or massive paracetamol overdosesPatientswho ingest large ormassive doses of paracetamolwere not discussed in previous versions of the guidelines.Most patients ingest less than 30 g of paracetamol, withonly a small percentage of overdoses having a paraceta-mol concentration greater than double the nomogramline. Those who ingest greater doses may have decreasedparacetamol clearance and increased risk of hepatotox-icity despite treatment, and may benefit from modifyingthe standard paracetamol management. Patients consid-ered at high risk of hepatotoxicity are those with highinitial paracetamol concentrations.

Angela L ChiewBSc(Med), MB BS, FACEM1,2

John S FountainMB ChB, MEntr3

Andis GraudinsMB BS, PhD, FACEM4,5

Geoffrey K IsbisterBSc, MD, FACEM6,7

David ReithFRACP, PhD3

Nicholas A BuckleyBMed, FRACP, MD2

1 Prince of Wales Hospital,Sydney, NSW.

2 University of Sydney,Sydney, NSW.

3 University of Otago,Dunedin, Otago,New Zealand.

4Monash University,Melbourne, VIC.

5Monash University andMonash Health, Dandenong,

VIC.

6 University of Newcastle,Newcastle, NSW.

7 Calvary Mater, Newcastle,NSW.

a_chiew@hotmail.com

doi: 10.5694/mja15.00614

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Guidelines Clinical focus

Although no randomised control trials have investi-gated optimum acetylcysteine dosage in these patients,it is the practice of many clinical toxicologists to adjustthe dose in large paracetamol overdoses. Who mightbenefit from an increase in acetylcysteine dose and theoptimum dose have not yet been determined. Oneapproach, in patients with a paracetamol concentrationmore than double the nomogram line, is to double theconcentration of the 16-hour infusion of acetylcysteinefrom 100 mg/kg (current standard acetylcysteine third-bag infusion) to 200 mg/kg intravenous acetylcysteine.Serum ALT and paracetamol levels should be checkednear the completion of acetylcysteine infusion. Ace-tylcysteine should be continued if the ALT level isincreasing (greater than 50 U/L) or the paracetamolconcentration is greater than 10 mg/L (66 mmol/L). ThePoisons Information Centre or a clinical toxicologistmay be consulted for the most current advice onmanaging these patients, including the optimal ace-tylcysteine regimen.

2 Management flow chart for acute paracetamol exposure with known time of ingestion

ALT ¼ serum alanine aminotransferase. u

1 Paracetamol dosing that may be associated with hepatic injury

Adults and children >6 yearsof age

Children (aged 0e6years)*

Acute singleingestion

> 200mg/kg over a periodof < 8 hours

Repeatedsupratherapeuticingestion

> 200 mg/kg over a single24-hour period

> 150 mg/kg per 24-hourperiod for the preceding48 hours

> 200 mg/kg or 10 g (whichever is lower) over a period of <8 hours

> 200 mg/kg or 10 g (whichever is lower) over a single 24-hour period

> 150 mg/kg or 6 g (whichever is lower) per 24-hour period for the preceding 48 hours

> 100 mg/kg or 4 g (whichever is lower) per 24-hour period, for more than 48 hours in those who also have symptoms indicating possible liver injury(eg, abdominal pain, nausea or vomiting)

> 100 mg/kg per 24-hourperiod for more than48 hours

* For obese children, the body weight used for calculations should be an ideal body weight. u

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Liquid paracetamol ingestion by childrenunder 6 years of ageNo recommendations were made in the previous guide-line. When ingestion of more than 200 mg/kg of liquidparacetamol by a child under 6 years of age is suspected(in obese children, this should be based on an ideal bodyweight), serum paracetamol concentration should bemeasured at least 2 hours after ingestion. If the concen-tration 2 to 4 hours after ingestion is less than 150 mg/L(1000 mmol/L), acetylcysteine is not required. If the2-hour paracetamol concentration is greater than

150 mg/L (1000 mmol/L), it should be measured again4 hours after ingestion, and acetylcysteine infusioncommenced if the value is still greater than 150 mg/L(1000 mmol/L), as per the paracetamol nomogram.

The 2-hour paracetamol concentration should only beused to guide management in a healthy child less than6 years of age, after an isolated liquid paracetamolingestion. In all other cases, such as children who presentlater than 4 hours after ingestion, and children who areolder than 6 years of age, treatment is the same as that foracute paracetamol exposure in adults.

3 Management flow chart for repeated supratherapeutic paracetamol ingestion

ALT ¼ serum alanine aminotransferase. u

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Guidelines Clinical focus

Repeated supratherapeutic ingestionPatients should have serum paracetamol and ALT con-centrations measured if they meet the criteria for supra-therapeutic ingestion (Box 1). The main changes in theguidelines concern the criteria for assessment in thosewho have ingestedmore than 100mg/kg/day or 4 g/day(whichever is lower) per 24-hour period for longer than48 hours. Patients only require assessment if they havesymptoms such as abdominal pain or nausea or vomiting.Management is outlined in Box 3.

Acetylcysteine dosing recommendationThe guideline essentially remains unchanged, except thatdosing should be based on actual body weight roundedup to the nearest 10 kg, with a ceiling weight of 110 kg.

HepatotoxicityThis was not discussed in detail in the previous guide-lines.Acetylcysteine should be continueduntil the patientis clinically improving, ALT levels are decreasing, theinternational normalised ratio (INR) is improving andless than 2, and the paracetamol concentration is less than10 mg/L (66 mmol/L). Regular clinical review and12-hourly (or more frequent) blood tests are recom-mended if there is clinical deterioration.

A liver transplant unit should be consulted if any of thefollowing criteria are met:

� INR > 3.0 at 48 hours or > 4.5 at any time;

� oliguria or creatinine > 200 mmol/L;

� persistent acidosis (pH < 7.3) or arterial lactate> 3 mmol/L;

� systolic hypotension with blood pressure less than80 mmHg, despite resuscitation;

� hypoglycaemia;

� severe thrombocytopenia;

� encephalopathy of any degree, or any alteration ofconsciousness (Glasgow coma scale < 15) not associ-ated with co-ingestion of sedatives.

Conclusions

This is a summary of the updated guidelines for themanagement of paracetamol poisoning in Australia andNew Zealand. The full guidelines are available onthe website of the Medical Journal of Australia (www.mja.com.au/sites/default/files/issues/203_05/Guidelines_paracetamol_Aus_NZ_2015.pdf).

Where there are any concerns regarding themanagementof paracetamol ingestion, advice can always be soughtfrom a clinical toxicologist or the Poisons InformationCentre (telephone: 13 1126 inAustralia, 0800 764 766 [0800POISON] in New Zealand).Acknowledgements: We thank Clinical Associate Professor Simone Strasser (RoyalPrince AlfredHospital) and transplant hepatologists fromaround Australia and the King’sCollege, London, for their input regarding patients requiring discussion with a livertransplant unit.

Competing interests: No relevant disclosures.

Provenance: Commissioned; not externally peer reviewed.n

ª 2015 AMPCo Pty Ltd. Produced with Elsevier B.V. All rights reserved.

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